Not Applicable.
Not Applicable.
1. Field of the Invention
This invention relates to matching tires to wheel rims and testing tires for acceptability, and more particularly to an improved system for improving tire acceptability.
2. Description of the Prior Art
Wheel balancers determine unbalance in vehicle wheel/tire assemblies by an analysis of the mechanical vibrations caused by rotating the wheel/tire assembly respectively. The mechanical vibrations are measured as motions, forces, or pressures by means of transducers, which convert the mechanical vibrations to electrical signals. Wheel/tire assembly unbalance may result from unbalance in the wheel, unbalance in the tire, or both.
Even when a wheel/tire assembly is balanced, non-uniformity in the construction of the tire as well as runout in the wheel rim can cause significant vibration forces as the wheel rolls under vehicle load. Most tire manufacturers inspect their tires on tire uniformity machines and grind rubber off the tires as required to improve rolling characteristics of the tires. Even after this procedure, tires will often produce vibration forces (not related to imbalance) of 20 pounds as they roll on a smooth road.
Despite improvement in balancing equipment over the years, it has been found that an unacceptably large number of tires are found to have excessive runout, even after matching the tire runout to that of available wheel rims.
Some of the deficiencies of prior art balancers are addressed by co-assigned U.S. application Ser. No. 09/311,473, which is incorporated herein by reference.
Among the various objects and features of the present invention the provision of method and apparatus which compensates for wheel rim and tire runout.
A second object is the provision of such a method and apparatus that increases the number of tires found to be acceptable after balancing.
A third object is the provision of such a method and apparatus which results in improved vibration reduction in the balanced wheel/tire assembly.
Other objects and features will be in part apparent and in part pointed out hereinafter.
Briefly, in a first aspect of the present invention a tire is matched to a wheel rim of a wheel to compensate for wheel rim run-out and tire force variations. The method of the invention includes mounting a bare wheel on a spindle of a balancer and measuring the rim run-out, said wheel rim having a bead seat, mounting a tire on the wheel to form a wheel/tire assembly, mounting the wheel/tire assembly on the spindle and measuring force variation of the wheel/tire assembly, determining a desired change in wheel rim run-out to reduce the wheel/tire assembly force variation, removing the tire from the wheel, adding a shim to the bead seat of the wheel rim, the shim being selected to correspond to the desired change in wheel rim run-out, and remounting the tire on the wheel.
In a second aspect of the present invention a wheel shim is provided for a wheel rim having a bead seat. The wheel shim is elongate and has a width sized to fit in the bead seat of the wheel rim. The thickness of the wheel shim is substantially less than the width of the wheel shim, and the length of the wheel shim is substantially greater than the width of the wheel shim. The wheel shim has a bottom surface adapted to be disposed in the bead seat and has a top surface adapted to be in contact with the bead of a tire to be mounted on the wheel.